Why do both ppl have grudge against opposing teams?

I’m usually the guy to mute the enemy team in my games but on the odd chance when I forget it’s always the both teams having an all out war with eachother first minute in the game. It usually goes like this One guy tries to tilt the enemy team The enemy team defends that one team mate and start trash talking back like come on. It’s a game why is it so necessary to ppl to hate eachother when they are on the enemy team. Like it’s really immature back when I used to be on a soccer team or any sports team no one had the urge to constantly hate on their opponents but in league like holy. Unlike competitive sports League is a video game and what are video games for? Having fun a lot of ppl play video games to have fun even if it’s something like league so if ur shit talking the enemy team or vice versa just because they’re ur opponents then stop, it spoils the game for ppl In conclusion Don’t be an asshole If no one is stopping then mute all